Supports for high surface area catalysts

ABSTRACT

The present invention relates to thermally stable, high surface area alumina supports and method of preparing such supports with at least one modifying agent. The method includes adding the modifying agent to the alumina prior to calcining. More particularly, the invention relates to the use of such catalysts for the catalytic partial oxidation of light hydrocarbons (e.g., methane or natural gas) to produce primarily synthesis gas. The present invention further relates to gas-to-liquids conversion processes, more specifically for producing C 5+  hydrocarbons.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of 35 U.S.C. 111(b)Provisional Application Serial No. 60/425,383 filed Nov. 11, 2002, andU.S. Provisional Application Serial No. 60/425,381 filed Nov. 11, 2002,entitled “Novel Syngas Catalysts and Their Method of Use” which arehereby incorporated by reference herein for all purposes. Thisapplication is related to the concurrently filed, commonly owned,co-pending U.S. Provisional Application Serial No. 60/501,185 filed Sep.8, 2003, entitled “Stabilized Alumina Supports, Catalysts MadeTherefrom, And Their Use in Partial Oxidation.”

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

TECHNICAL FIELD OF THE INVENTION

[0003] The present invention generally relates to catalyst supportshaving high surface area and stability in ultra high temperatureconditions. This invention more particularly relates to modified aluminasupports and catalysts made therefrom that maintain high surface areasat high temperature reaction conditions. The present invention alsorelates to processes employing these catalysts for the catalyticconversion of light hydrocarbons (e.g., natural gas) to produce carbonmonoxide and hydrogen (synthesis gas), and conversion of synthesis gasto hydrocarbons. This invention also discloses methods of making suchsupports and catalysts.

BACKGROUND OF THE INVENTION

[0004] It is well known that the efficiency of catalyst systems is oftenrelated to the surface area on the support. This is especially true forsystems using precious metal catalysts or other expensive catalysts. Thegreater the surface area, the more catalytic material is exposed to thereactants and the less time and catalytic material is needed to maintaina high rate of productivity.

[0005] Alumina (Al₂O₃) is a well known support for many catalystsystems. It is also well known that alumina has a number of crystallinephases such as alpha alumina (often noted as α-alumina or α-Al₂O₃),gamma alumina (often noted as γ-alumina or γ-Al₂O₃) as well as a myriadof others. One of the properties of gamma alumina is that it has a veryhigh surface area. This is commonly believed to be because the aluminumand oxygen molecules are in a crystalline structure or form that is notvery densely packed. Unfortunately, when gamma alumina is heated to hightemperatures, the structure of the atoms collapses such that the surfacearea decreases substantially. The most dense crystalline form of aluminais alpha alumina. Thus, alpha alumina has the lowest surface area, butis the most stable at high temperatures.

[0006] Alumina is ubiquitous as supports and/or catalysts for manyheterogeneous catalytic processes. Some of these catalytic processesoccur under conditions of high temperature, high pressure and/or highwater vapor pressure.

[0007] It has long been a desire of those skilled in the catalystsupport arts to create a form of alumina that has high surface area likegamma alumina and stability at high temperature like alpha alumina.

[0008] Such a catalyst support would have many uses. One such use is inthe production of synthesis gas in a catalytic partial oxidationreactor. Synthesis gas is primarily a mixture of hydrogen and carbonmonoxide and can be made from the partial burning of light hydrocarbonswith oxygen. The hydrocarbons, such as methane or ethane are mixed withoxygen or oxygen containing gas and heated. When the mixture comes incontact with an active catalyst material at a temperature above aninitiation temperature, the reactants quickly react generating synthesisgas and a lot of heat. Catalytic partial oxidation is a very fastreaction requiring only milliseconds of contact of reactant gases withthe catalyst. As a result, it is quite exothermic causing reactortemperatures to exceed 800° C., often going above 1000° C. and evensometimes going above 1200° C. Since catalysts used in the partialoxidation of hydrocarbons is typically supported, the support should beable to sustain this high thermal condition during long-term operation.In other words, a stable catalyst support which retains most of itssurface area is desirable for long catalyst life.

[0009] The selectivity of catalytic partial oxidation of lighthydrocarbons to the desired products, carbon monoxide and hydrogen, areinfluenced by several factors, but one of the most important of thesefactors is the catalyst composition. Noble metals typically serve as thebest catalysts for the partial oxidation of methane. Noble metals arehowever scarce and expensive, making their use economically challengingespecially when the stability of the catalyst is questionable. One ofthe better known noble metal catalysts for catalytic partial oxidationis Rhodium. Rhodium-based syngas catalysts deactivate very fast due tosintering of both catalyst support and/or metal particles. Prevention ofany of these undesirable phenomena is well-sought after in the art ofcatalytic partial oxidation process, particularly for successful andeconomical operation at commercial scale.

[0010] Another use for a highly stabilized, high surface area catalystsupport would be in catalytic reactions that produce high temperaturewater vapor at high partial pressures. Such an environment challengesthe hydrothermal stability of alumina supports making the supports moreprone to degradation, fragmentation, or other processes that compromisethe ability to support catalytic metals. For purposes of the presentdiscussion, hydrothermal stability is defined as the property ofresisting morphological and/or structural change in the face of elevatedheat and water vapor pressure.

[0011] The Fischer-Tropsch process (also called the Fischer-Tropschreaction or Fischer-Tropsch synthesis) is an example of a process thatcan generate water vapor of high partial pressure at high temperatures.The Fischer-Tropsch process comprises contacting a feed streamcomprising syngas with a catalyst comprising typically a Group VIIImetal at conditions of elevated pressure and temperature to producemixtures of hydrocarbons and by-products comprising water and oxides ofcarbon. Syngas can be provided to a Fischer-Tropsch process from severalsources such as the gasification of coal; from natural gas reservesusing a partial oxidation process with an oxygen source; or by reactionof natural gas with steam (steam reforming).

[0012] It would therefore be highly desirable to create athermally-stable high surface area support with a Group VIII metalloaded onto the support for highly productive long lifetime catalystsfor the syngas production and/or its conversion to hydrocarbons.

SUMMARY OF THE INVENTION

[0013] The present invention is a thermally stable, high surface areaalumina support with at least one modifying agent. The modifying agentis at least one element selected from the group consisting of aluminum,boron, silicon, gallium, selenium, rare earth metals, alkali earthmetals and transition metals, and their corresponding oxides and ions.The inventive support has thermal stability at temperatures above 800°C.

[0014] The present invention also includes the process for stabilizing ahigh surface area alumina support. The process for stabilizing thesupport includes adding at least one modifying agent to the aluminaprior to calcining. The modifying agents include aluminum, boron,silicon, gallium, selenium, rare earth metals, alkali earth metals andtransition metals.

[0015] The invention further includes a catalyst comprising acatalytically active metal on alumina support wherein the supportincludes at least one modifying agent. The modifying agent comprises atleast one element selected from the group consisting of aluminum, boron,silicon, gallium, selenium, a rare earth metal, an alkali earth metal ora transition metal, their corresponding oxides or ions.

[0016] The present invention can be more specifically seen as a support,process and catalyst wherein the preferred modifying agents arelanthanide metals, aluminum, silicon, magnesium, calcium, manganese,cobalt, iron, zirconia, their oxides, their ions, or combinationsthereof. The supported catalyst comprises at least one group VIII metalor rhenium with an optional promoter.

[0017] A more specific embodiment of the invention is a catalyst havinga high surface area thermally stable alumina support with at least onegroup VIII metal or rhenium and an optional promoter loaded onto thesupport. Another specific embodiment of the invention is a catalysthaving a high surface area hydro-thermally stable alumina supportmodified with aluminum with at least one group VIII metal and anoptional promoter loaded onto the support.

[0018] More particularly, the invention relates to processes for thecatalytic partial oxidation of light hydrocarbons (e.g., methane ornatural gas) to produce primarily synthesis gas and the use of suchsupported catalysts to make carbon monoxide and hydrogen underconditions of high gas hourly space velocity, elevated pressure and hightemperature.

[0019] The present invention further relates to Fischer-Tropschcatalysts and processes for the conversion of syngas for producing C₅₊hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a more detailed understanding of the preferred embodiments,reference is made to the accompanying drawings, wherein:

[0021]FIG. 1 represents the pore distribution of unmodified Al₂O₃ andseveral examples of modified Al₂O₃;

[0022]FIG. 2 represents X-ray diffraction traces of the unmodified Al₂O₃and several modified Al₂O₃ after calcinations at 1100° C.; and

[0023]FIG. 3 represents the performance data for syngas production froma catalyst made according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] Herein will be described in detail, specific embodiments of thepresent invention, with the understanding that the present disclosure isto be considered an exemplification of the principles of the invention,and is not intended to limit the invention to that illustrated anddescribed herein. The present invention is susceptible to embodiments ofdifferent forms or order and should not be interpreted to be limited tothe specifically expressed methods or compositions contained herein. Inparticular, various embodiments of the present invention provide anumber of different configurations of the overall gas to liquidconversion process.

[0025] The present invention provides a modified alumina support withenhanced thermal stability and with a high BET surface area greater than5 m²/g, preferably greater than 10 m²/g, and preferably greater than 15m²/g. The modified alumina support is obtained by deposition of at leastone modifying agent. The modifying agent comprises at least one elementselected from the group consisting of aluminum, boron, silicon, gallium,selenium, rare earth metals, transition metals, alkali earth metals, andtheir corresponding oxides or ions, preferably selected from the groupconsisting of alumina (Al), boron (B), silicon (Si), gallium (Ga),selenium (Se), calcium (Ca), lanthanum (La), cerium (Ce), praseodymium(Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu),gadolinium (Gd), terbium (Th), dysprosium (Dy), holmium (Ho), erbium(Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), zirconium (Zr), iron,(Fe), cobalt (Co), manganese (Mn), magnesium (Mg), and theircorresponding oxides or ions. More preferably the modifying agentcomprises La, Al, Sm, Pr, Ce, Eu, Yb, Si, Ce, Mg, Ca, Mn, Co, Fe, Zr,their corresponding oxides or ions, or any combinations thereof. Mostpreferably the modifying agent comprises La, Al, Sm, Pr, Ce, Eu, Yb, Si,Mg, Co, their corresponding oxides or ions, or any combinations thereof.

[0026] The present invention provides a method of making a modifiedalumina support with a modifying agent. The method comprises thedeposition of the modifying agent followed by a high temperaturetreatment. The high temperature treatment is a calcination at atemperature greater than 400° C. The calcination temperature is selectedbased on the highest temperature the catalyst would likely experience inoperation, i.e. the catalytic reactor. Thus, if the catalytic system isanticipated to operate at a temperature above 800° C., the calcinationtemperature would be greater than 600° C., preferably between 800° C.and 1400° C., more preferably between 900° C. and 1300° C. If thecatalytic system is anticipated to operate at less 800° C., thecalcination range would preferably be between about 400° C. and 800° C.,more preferably between 450° C. and 750° C.

[0027] In preferred embodiments the stabilized support is made by amethod that comprises combining the modifying agent or a precursorthereof with an alumina material or a precursor of an alumina materialin an amount sufficient to deter disintegration or structuraldeterioration of the alumina material during the partial oxidizationprocess. In certain embodiments the combined modifying agent and aluminamaterial form a solid solution between the modifying agent and at leasta portion of the support material. As a result, a modifier-supportintermediate structure is obtained. In certain preferred embodiments thestabilized support comprises, at least in part, a crystalline structurethat is capable of resisting a phase change at temperatures up to atleast 1,200° C. The modifying agent may comprise, for example, La, Al,Sm, Pr, Ce, Eu, Yb, Si, Mg, Co, Ca, Mn, Fe or Zr.

[0028] In certain embodiments the syngas catalyst is prepared by amethod that comprises calcining the modifier-support intermediate at atemperature in the operating temperature range of the catalyst when thecatalyst is used in a reactor for catalyzing the partial oxidation ofthe light hydrocarbon to form carbon monoxide and hydrogen. After thecatalytic material is deposited on the stabilized support, it may bereduced by subjecting the catalyst to reducing conditions. In someembodiments, the catalytic material comprises rhodium, and in certainembodiments comprises a rhodium alloy such as Rh—Ru or Rh—Ir, forexample.

[0029] In certain embodiments the modifying agent comprises 0.1-10 wt %of the catalyst, and in some embodiments it comprises 1-5 wt % of thecatalyst. In some embodiments, the modifying agent comprises cobalt,magnesium, or silicon, and in some embodiments the modifying agentcomprises lanthanum.

[0030] Modifying alumina (Al₂O₃) with some rare earth metals has beenproven to be effective in stabilizing the surface area of modifiedAl₂O₃. It was discovered by the Applicants that doping a γ-Al₂O₃ withlanthanum oxide (La₂O₃) inhibits or retards the phase transformation ofγ phase to θ phase and eventually to a phase and thus stabilizes thesurface area and pore structure of the alumina material even at highcalcination temperatures above 1000° C.

[0031] The support can have different forms such as monolith orparticulate or have discrete or distinct structures. The term “monolith”as used herein is any singular piece of material of continuousmanufacture such as solid pieces of metal or metal oxide or foammaterials or honeycomb structures. The terms “distinct” or “discrete”structures or units, as used herein, refer to supports in the form ofdivided materials such as granules, beads, pills, pastilles, pellets,cylinders, trilobes, extrudates, spheres or other rounded shapes, oranother manufactured configuration. Alternatively, the divided materialmay be in the form of irregularly shaped particles. Preferably at leasta majority (i.e., >50%) of the particles or distinct structures have amaximum characteristic length (i.e., longest dimension) of less than sixmillimeters, preferably less than three millimeters. An especiallypreferred particle size range is about 0.18 millimeters (80 mesh) toabout 3 millimeters, more preferably about 0.3-1.4 millimeters (about14-50 mesh). The term “mesh” refers to a standard sieve opening in ascreen through which the material will pass, as described in the TylerStandard Screen Scale (C. J. Geankoplis, TRANSPORT PROCESSES AND UNITOPERATIONS, Allyn and Bacon, Inc., Boston, Mass., p. 837), herebyincorporated herein by reference. Mesh size of the particles or distinctstructures can be measured by the ASTM E-11-61 method.

[0032] The present invention also relates to improved catalystcompositions using a modified alumina support, as well as methods ofmaking and using them. In particular, some embodiments of the presentinvention comprise high melting point catalysts comprising metal alloys.

[0033] The catalyst is supported on a modified alumina with a minimumBET surface area of 5 m²/g, preferably greater than 10 m²/g, morepreferably greater than 15 m²/g after high heat treatment. Preferablythe modified alumina is modified with aluminum, cobalt, magnesium,silicon, a lanthanide metal, their respective oxide or ion such as forexample, aluminum, lanthanum, samarium, cobalt, magnesium, silicon, ortheir respective oxide or ion. Without wishing to be bound to aparticular theory, the Applicants believe that the metal-supportinteraction in catalysts supported on for example La₂O₃-modified Al₂O₃is stronger than that in the catalyst supported on unmodified Al₂O₃, andthat this strong metal-support interaction in La₂O₃-modified Al₂O₃supported catalysts might be responsible for the unusually high catalyststability.

[0034] The catalyst used for producing synthesis gas comprises an activemetal selected from the group consisting of Group VIII metals, rhenium,tungsten, zirconium, molybdenum, and any mixtures thereof. Preferablythe catalyst used for producing synthesis gas comprises rhodium (Rh),ruthenium (Ru), iridium (fr), rhenium (Re) or any combination thereof.In some embodiments, the active metal is comprised in an alloy form,preferably a rhodium alloy. Although not wishing the scope of thisapplication to be limited to this particular theory, the Applicantsbelieved that alloying rhodium with other metals appears to sustain theresistance of rhodium catalysts to sintering, and therefore to allow theRh alloy catalysts to deactivate at a slower rate than syngas catalystscontaining only rhodium. Suitable metals for the rhodium alloy generallyinclude but are not limited to Group VIII metals, as well as rhenium,tantalum, niobium, molybdenum, tungsten, zirconium and mixtures thereof.The preferred metals for alloying with rhodium are ruthenium, iridium,platinum, palladium, tantalum, niobium, molybdenum, rhenium, tungsten,cobalt, and zirconium, more preferably ruthenium, rhenium, and iridium.

[0035] The catalyst used for converting synthesis gas comprises anactive metal selected from Group VIII. Preferably the catalyst used forconverting synthesis gas comprises cobalt, iron, ruthenium, nickel orany combination thereof. In preferred embodiments, the modifying agentis aluminum or an oxide or ion of aluminum.

[0036] In accordance with the present invention, the loading of theactive metal is preferably between 0.1 and 50 weight percent of thetotal catalyst weight (herein wt %).

[0037] In one embodiment of the invention the active metal is rhodium,which comprises from about 0.1 to about 20 wt % of the catalystmaterial, preferably from about 0.5 to about 10 wt %, and morepreferably from about 0.5 to about 5 wt %. When a rhodium alloy is used,the other metal in the rhodium alloy preferably comprises from about 0.1to about 20 wt % of the catalyst material, preferably from about 0.5 toabout 10 wt %, and more preferably from about 0.5 to about 5 wt %.

[0038] When the active metal is cobalt, nickel, or iron, the metalcomprises from about 0.1 to 50 wt % of the catalyst material, preferablyfrom about 5 to about 40 wt %, and more preferably from about 10 toabout 35 wt %.

[0039] In another embodiment of the invention the active metal isruthenium which comprises from about 0.1 to 15 wt % of the catalystmaterial, preferably from about 1 to about 8 wt %, and more preferablyfrom about 2 to about 5 wt %.

[0040] The catalyst structure employed is characterized by having a highmetal surface area, i.e., at least 0.8 square meters of metal per gramof catalyst structure, preferably at least 1 m²/g. Preferably the metalis rhodium and the rhodium surface area at least 0.8 square meters ofrhodium per gram of supported catalyst, preferably at least 1 m²/g.

[0041] Catalyst compositions may also contain one or more promoters. Insome embodiments when one active metal is rhodium, rhenium, ruthenium,or iridium, the promoter comprises an element selected from the groupconsisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb andLu, preferably Sm, Eu, Pr and Yb. The Applicants discovered that theintroduction of a lanthanide oxide, especially Sm₂O₃, on the modifiedalumina support surface before deposition of active metal(s) seems tofurther enhance the metal-support interaction, and that the activemetal(s) also disperses better on the surface of Al₂O₃ modified withLa₂O₃ and/or Sm₂O₃. According to some embodiments with the use of arhodium alloy, the presence of a promoter metal can be omitted withoutdetriment to the catalyst activity and/or selectivity. It is foreseeablehowever that, in some alternate embodiments, a promoter could be addedto a catalyst material comprising a rhodium alloy. In other embodimentsthe active metal is cobalt, ruthenium, iron, or nickel, and the promoteris selected from the group consisting of the alkali metals, the alkalineearths, the lanthanides, Group IIIB, IVB, VB, VIB and VIIB metals.Promoters, when used, preferably comprise about 1-15 wt % of thecatalyst composition.

[0042] In one embodiment of the present invention is more preferablydirected towards syngas catalysts used in partial oxidation reactionsand even more preferably used in syngas catalysts that contain solelyrhodium or rhodium alloys. However, it should be appreciated that thecatalyst compositions according to the present invention are useful forother partial oxidation reactions, which are intended to be within thescope of the present invention.

[0043] In another embodiment of the present invention the catalystsupport is used for hydrogenation catalysts in conversion of syngas toalcohols or C₅₊ hydrocarbons via the Fischer-Tropsch reaction. Inaddition, the present invention contemplates an improved method forconverting hydrocarbon gas to liquid hydrocarbons using the novel syngascatalyst compositions described herein. Thus, the invention also relatesto processes for converting hydrocarbon-containing gas to liquidproducts via an integrated syngas to Fischer-Tropsch, methanol or otherprocess.

[0044] Method of Reparation of Catalyst Support

[0045] The present invention further presents a method of making asyngas catalyst support wherein said method comprises depositing acompound or precursor of a modifying agent onto an alumina precursor;calcining the deposited alumina precursor at temperatures temperaturegreater than 600° C., preferably between 800° C. and 1400° C., morepreferably between 900° C. and 1300° C. to form a modified alumina.

[0046] The present invention further presents a method of making aFischer-Tropsch catalyst support wherein said method comprisesdepositing a compound or precursor of a modifying agent onto an aluminaprecursor; calcining the deposited alumina precursor at temperaturestemperature between 300° C. and 1000° C., and more preferably at atemperature between 400° C. and 800° C. to form a modified alumina.

[0047] The alumina precursor can comprise one or more alumina phasessuch as, but not limited to, gamma, delta, kappa, theta, alpha that areknown in the art. The alumina precursor can also comprise Boehmitealumina or pseudoboehmite. An alumina precursor comprising mainlyγ-alumina is preferred. It should be understood that the aluminaprecursor could be pre-treated prior to deposition of the modifyingagent. The pre-treatment could be heating, spraydrying (to e.g., adjustparticle sizes) dehydrating, drying, steaming or calcining. Steaming thealumina precursor can be done at conditions sufficient to transform thealumina precursor into a hydrated from of aluminum oxide, such asboehmite or pseudoboehmite.

[0048] The present process for preparing a modified alumina may furthercomprise steaming the deposited alumina precursor at conditionssufficient to transform the deposited alumina precursor into a modifiedboehmite alumina wherein steaming is defined as subjecting a givenmaterial, within the confines of an autoclave or other suitable device,to an atmosphere comprising a saturated or under-saturated water vaporat conditions of elevated temperature and elevated water partialpressure.

[0049] In one aspect, the steaming of the deposited alumina precursor ispreferably performed at a temperature ranging from 150° C. to 500° C.,more preferably ranging from 180° C. to 300° C., and most preferablyranging from 200° C. to 250° C.; a water vapor partial pressurepreferably ranging from 1 bar to 40 bars, more preferably ranging from 4bars to 20 bars, and most preferably from 10 bars to 20 bars; and aninterval of time preferably from 0.5 hour to 10 hours, and mostpreferably 0.5 hour to 4 hours. Preferably, under these steamingconditions, the deposited alumina precursor is at least partiallytransformed to at least one phase selected from the group boehmite,pseudoboehmite and the combination thereof. A pseudoboehmite aluminarefers to a monohydrate of alumina having a crystal structurecorresponding to that of boehmite but having low crystallinity orultrafine particle size. Alternatively, the optional steaming of thedeposited alumina precursor may comprise same conditions of temperatureand time as above, but with a reduced water vapor partial pressurepreferably ranging from 1 bar to 5 bar, and more preferably ranging from2 bars to 4 bars.

[0050] The compound or precursor of a modifying agent can be in the formof salt, acid, oxide, hydroxide, oxyhydroxide, carbide, and the like.Preferably the compound or precursor of a modifying agent is an oxide ora salt (such as carbonate, acetate, nitrate, chloride, or oxalate). Themodifying agent comprises at least one element selected from the groupconsisting of aluminum, boron, silicon, gallium, selenium, rare earthmetals, transition metals, alkali earth metals, their correspondingoxides or ions, preferably at least one element selected from the groupconsisting of Al, B, Si, Ga, Se, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy,Ho, Er, Tm, Yb, Lu, and their corresponding oxides or ions. Morepreferably, the modifying agent comprises either La, Al, Pr, Ce, Eu, Yb,or Sm, or their corresponding oxides or ions, or any combinationsthereof. Preferably the compound or precursor of a modifying agent is anitrate salt or a chloride salt, as for example only La(NO₃)₃, orAl(NO₃). It should be understood that more than one modifying agent ormore than one compound or precursor of a modifying agent can be used.

[0051] The modifying agent can be deposited into the alumina precursorby means of different techniques. For example only, deposition methodscan be spraydrying, impregnation, co-precipitation, chemical vapordeposition, and the like. It should also be understood that anycombination of techniques or multiple steps of the same technique can beused to deposit a modifying agent. One preferred technique fordepositing the modifying agent is impregnation, particularly incipientwetness impregnation.

[0052] When the deposition is done via impregnation, optionally a dryingstep at temperatures between 75° C. and 150° C. is performed on thedeposited alumina prior to calcination. In another embodiment, themodified support is derived from the alumina precursor by contacting thealumina precursor with the modifying agent so as to form a supportmaterial and treating the support material so as to form ahydrothermally stable support. Contacting the alumina precursor with thestructural stabilizer preferably includes dispersing the aluminaprecursor in a solvent so as to form a sol, adding a compound of themodifying agent to the sol, and spraydrying the sol so as to form thesupport material. It should be understood that more than one modifyingagents or more than one compound or precursors of a modifying agent canbe added to the sol. Alternatively, one modifying agent can beincorporated into the support by means of the aforementioned techniques.Alternatively, two or more modifying agents can be incorporated into thesupport by means of the aforementioned techniques.

[0053] Method of Catalyst Preparation

[0054] The present invention further presents a method of making asyngas catalyst wherein said method comprises optionally depositing acompound or precursor of one or more promoters to the modified aluminaand calcining the (deposited) modified alumina at temperatures greaterthan 600° C., preferably between about 800° C. and about 1400° C., morepreferably between about 900° C. and about 1300° C. to form a catalystprecursor; depositing a compound or precursor of one or more activemetals to the catalyst precursor; calcining the deposited catalystprecursor at temperatures between about 300° C. and about 1200° C.,preferably between about 500° C. and about 1100° C.

[0055] The compound or precursor of the promoter can be in the form ofsalt, acid, oxide, hydroxide, oxyhydroxide, carbide, and the like.Preferably the compound or precursor of a promoter is a salt. Thepromoter comprises at least one element selected from the groupconsisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb,Lu, and their corresponding oxides or ions. Preferably the promotercomprises either Pr, Yb, Eu, Sm, their corresponding oxides or ions, orany combinations thereof. Preferably the compound or precursor of apromoter is a nitrate salt, as for example only Sm(NO₃)₃ or La(NO₃). Itshould be understood that more than one promoter or more than onecompound or precursor of a promoter can be used.

[0056] The present invention further includes a method of making a FTcatalyst wherein said method comprises optionally depositing a compoundor precursor of one or more promoters to the modified alumina andcalcining the (deposited) modified alumina at temperatures greater than250° C., preferably between about 300° C. and about 800° C. to form acatalyst precursor; depositing a compound or precursor of one or moreactive metals to the catalyst precursor; calcining the depositedcatalyst precursor at temperatures between about 250° C. and about 800°C., preferably between about 300° C. and about 800° C. The promotercomprises at least one element selected from the group consisting ofalkali metals, the alkaline earths, the lanthanides, Group IIIB, IVB,VB, VIB and VIIB metals, their corresponding oxides or ions, or anymixtures thereof. Preferably, the promoter comprises either Pt, Pd, Re,Ru, Ag, B, Au, Cu, their corresponding oxides or ions, or anycombinations thereof. The compound or precursor of the promoter can bein the form of salt, acid, oxide, hydroxide, oxyhydroxide, carbide, andthe like. Preferably the compound or precursor of a promoter is a salt,for example only Co(NO₃)₃.

[0057] The promoter can be deposited into the modified alumina by meansof different techniques. For example only, deposition methods can beimpregnation, co-precipitation, chemical vapor deposition, and the like.The preferred technique for depositing the promoter is impregnation.

[0058] When the deposition of the promoter is done via impregnation,optionally a drying step at temperatures between 75° C. and 150° C. isperformed on the deposited modified alumina prior to calcination.

[0059] The compound or precursor of the active metal can be in the formof salt, acid, oxide, hydroxide, oxyhydroxide, carbide, and the like.Preferably the compound or precursor of the active metal is a salt. Theactive metal comprises one element selected from the group consisting ofGroup VIII metals, rhenium, tungsten, zirconium, their correspondingoxides or ions, and any combinations thereof. Preferably the activemetal for syngas catalyst comprises either rhodium, iridium, ruthenium,their corresponding oxides or ions, or any combinations thereof.Preferably the compound or precursor of the active metal is a nitrate ora chloride salt, as for example only Rh(NO₃)₃ or RhCl₃. Preferably theactive metal for FT catalyst comprises either cobalt, ruthenium, iron,nickel, their corresponding oxides or ions, or any combinations thereof.It should be understood that more than one active metal or more than onecompound or precursor of an active metal can be used. When two activemetals are used in the syngas catalyst, it is preferred that at leastrhodium is selected as one metal, that the other metal is selected fromthe active metal list above for syngas catalyst, and that the loading ofboth metals is such so as to form a rhodium alloy.

[0060] The active metal can be deposited on the catalyst precursor(promoted or unpromoted modified alumina) by means of differenttechniques. For example only, deposition methods can be impregnation,co-precipitation, chemical vapor deposition, and the like. The preferredtechnique for depositing the active metal is impregnation.

[0061] When the deposition of the active metal is done via impregnation,optionally a drying step at temperatures between 75° C. and 150° C. isperformed on the deposited catalyst precursor prior to calcination.

[0062] Process of Producing Syngas

[0063] According to the present invention, a syngas reactor can compriseany of the synthesis gas technology and/or methods known in the art. Thehydrocarbon-containing feed is almost exclusively obtained as naturalgas. However, the most important component is generally methane. Naturalgas comprise at least 50% methane and as much as 10% or more ethane.Methane or other suitable hydrocarbon feedstocks (hydrocarbons with fourcarbons or less) are also readily available from a variety of othersources such as higher chain hydrocarbon liquids, coal, coke,hydrocarbon gases, etc., all of which are clearly known in the art.Preferably, the feed comprises at least about 50% by volume methane,more preferably at least 80% by volume, and most preferably at least 90%by volume methane. The feed can also comprise as much as 10% ethane.Similarly, the oxygen-containing gas may come from a variety of sourcesand will be somewhat dependent upon the nature of the reaction beingused. For example, a partial oxidation reaction requires diatomic oxygenas a feedstock, while steam reforming requires only steam. According tothe preferred embodiment of the present invention, partial oxidation isassumed for at least part of the syngas production reaction.

[0064] Regardless of the source, the hydrocarbon-containing feed and theoxygen-containing feed are reacted under catalytic conditions. Improvedcatalyst compositions in accordance with the present invention aredescribed herein. They generally are comprised of a catalytic metal,some alloyed, that has been reduced to its active form and with one ormore optional promoters on a modified alumina support structure.

[0065] It has been discovered that the modification of alumina by amodifying agent selected from the lanthanide metals group particularly,results in a catalytic support suitable for high-temperature reactionssuch as syngas production via partial oxidation.

[0066] The syngas catalyst compositions according to the presentinvention comprise an active metal selected from the group consisting ofGroup VIII metals, rhenium, tungsten, zirconium, their correspondingoxides or ions, and any combinations thereof, preferably a group VIImetal or rhenium, more preferably rhodium, indium, ruthenium, rhenium,or combinations thereof.

[0067] In some embodiments when the active metal is rhodium, rhodium iscomprised in a high melting point alloy with another metal. It has beendiscovered that in addition to the enhanced thermal stability of thesupport, the high melting point rhodium alloys used in some of thesesyngas catalysts confer additional thermally stability than non-alloyrhodium catalysts, which leads to enhanced ability of the catalyst toresist various deactivation phenomena.

[0068] It is well known that during syngas reactions, several undesiredprocesses, such as coking (carbon deposition), metal migration, andsintering of metal and/or the support, can occur and severelydeteriorate catalytic performance. The catalyst compositions of thepresent invention are better able to resist at least one of thesephenomena over longer periods of time than prior art catalysts. As aconsequence, these novel rhodium containing catalysts on modifiedalumina can maintain high methane conversion as well as high CO and H₂selectivity over extended periods of time with little to no deactivationof the syngas catalyst.

[0069] The support structure of these catalysts can be in the form of amonolith or can be in the form of divided or discrete structures orparticulates. Particulates are preferred. Small support particles tendto be more useful in fluidized beds. Preferably at least a majority(i.e., >50%) of the particles or distinct structures have a maximumcharacteristic length (i.e., longest dimension) of less than sixmillimeters, preferably less than three millimeters. According to someembodiments, the divided catalyst structures have a diameter or longestcharacteristic dimension of about 0.25 mm to about 6.4 mm (about{fraction (1/100)}″ to about ¼″), preferably between about 0.5 mm andabout 4.0 mm. In other embodiments they are in the range of about 50microns to 6 mm.

[0070] The hydrocarbon feedstock and the oxygen-containing gas may bepassed over the catalyst at any of a variety of space velocities. Spacevelocities for the process, stated as gas hourly space velocity (GHSV),are in the range of about 20,000 to about 100,000,000 hr⁻¹, morepreferably of about 100,000 to about 800,000 hr⁻¹, most preferably ofabout 400,000 to about 700,000 hr⁻¹. Although for ease in comparisonwith prior art systems space velocities at standard conditions have beenused to describe the present invention, it is well recognized in the artthat residence time is the inverse of space velocity and that thedisclosure of high space velocities corresponds to low residence timeson the catalyst. “Space velocity,” as that term is customarily used inchemical process descriptions, is typically expressed as volumetric gashourly space velocity in units of hr⁻¹. Under these operating conditionsa flow rate of reactant gases is maintained sufficient to ensure aresidence or dwell time of each portion of reactant gas mixture incontact with the catalyst of no more than 200 milliseconds, preferablyless than 50 milliseconds, and still more preferably less than 20milliseconds. A contact time less than 10 milliseconds is highlypreferred. The duration or degree of contact is preferably regulated soas to produce a favorable balance between competing reactions and toproduce sufficient heat to maintain the catalyst at the desiredtemperature.

[0071] In order to obtain the desired high space velocities, the processis operated at atmospheric or superatmospheric pressures. The pressuresmay be in the range of about 100 kPa to about 32,000 kPa (about 1-320atm), preferably from about 200 kPa to about 10,000 kPa (about 2-100atm).

[0072] The process is preferably operated at a temperature in the rangeof about 350° C. to about 2,000° C. More preferably, the temperature ismaintained in the range 400° C.-2,000° C., as measured at the reactoroutlet.

[0073] The catalysts of the present invention should maintainhydrocarbon conversion of equal to or greater than about 85%, preferablyequal to or greater than about 90% after 100 hours of operation whenoperating at pressures of greater than 2 atmospheres. Likewise, thecatalysts of the present invention should maintain CO and H2 selectivityof equal to or greater than about 85%, preferably equal to or greaterthan about 90% after 100 hours of operation when operating at pressuresof greater than 2 atmospheres.

[0074] The synthesis gas product contains primarily hydrogen and carbonmonoxide, however, many other minor components may be present includingsteam, nitrogen, carbon dioxide, ammonia, hydrogen cyanide, etc., aswell as unreacted feedstock, such as methane and/or oxygen. Thesynthesis gas product, i.e., syngas, is then ready to be used, treated,or directed to its intended purpose. The product gas mixture emergingfrom the syngas reactor may be routed directly into any of a variety ofapplications, preferably at pressure. For example, in the instant casesome or all of the syngas can be used as a feedstock in subsequentsynthesis processes, such as Fischer-Tropsch synthesis, alcohol(particularly methanol) synthesis, hydrogen production,hydroformylation, or any other use for syngas. One preferred suchapplication for the CO and H₂ product stream is for producing, via theFischer-Tropsch synthesis, higher molecular weight hydrocarbons, such asC₅₊ hydrocarbons.

[0075] Syngas is typically at a temperature of about 600-1500° C. whenleaving a syngas reactor. The syngas must be transitioned to be useablein a Fischer-Tropsch or other synthesis reactors, which operate at lowertemperatures of about 200° C. to 400° C. The syngas is typically cooled,dehydrated (i.e., taken below 100° C. to knock out water) and compressedduring the transition phase. Thus, in the transition of syngas from thesyngas reactor to for example a Fischer-Tropsch reactor, the syngasstream may experience a temperature window of 50° C. to 1500° C.

[0076] Fischer-Tropsch Synthesis

[0077] The synthesis reactor using synthesis gas as feedstock ispreferably a Fischer-Tropsch reactor. The Fischer-Tropsch reactor cancomprise any of the Fischer-Tropsch technology and/or methods known inthe art. The Fischer-Tropsch feedstock is hydrogen and carbon monoxide,i.e., syngas. The hydrogen to carbon monoxide molar ratio is generallydeliberately adjusted to a desired ratio of approximately 2:1, but canvary between 0.5 and 4. The syngas is then contacted with aFischer-Tropsch catalyst. Fischer-Tropsch catalysts are well known inthe art and generally comprise a catalytically active metal, a promoterand a support structure. The most common catalytic metals are Group VIIImetals, such as cobalt, nickel, ruthenium, and iron or mixtures thereof.The support is generally alumina, titania, zirconia, silica, or mixturesthereof. In some embodiments, the catalyst is supported on a modifiedalumina as described in this invention. The preferred modifying agent isaluminum. Fischer-Tropsch reactors use fixed and fluid type conventionalcatalyst beds as well as slurry bubble columns. The literature isreplete with particular embodiments of Fischer-Tropsch reactors andFischer-Tropsch catalyst compositions. As the syngas feedstock contactsthe catalyst, the hydrocarbon synthesis reaction takes place. TheFischer-Tropsch product contains a wide distribution of hydrocarbonproducts from C₅ to greater than C₁₀₀. The Fischer-Tropsch process istypically run in a continuous mode. In this mode, the gas hourly spacevelocity through the reaction zone typically may range from about 50 toabout 10;000 hr⁻¹, preferably from about 300 hr⁻¹ to about 2,000 hr⁻¹.The gas hourly space velocity is defined as the volume of reactants pertime per reaction zone volume. The volume of reactant gases is atstandard pressure of 1 atm or 101 kPa and standard temperature of 0° C.The reaction zone volume is defined by the portion of the reactionvessel volume where reaction takes place and which is occupied by agaseous phase comprising reactants, products and/or inerts; a liquidphase comprising liquid/wax products and/or other liquids; and a solidphase comprising catalyst. The reaction zone temperature is typically inthe range from about 160° C. to about 300° C. Preferably, the reactionzone is operated at conversion promoting conditions at temperatures fromabout 190° C. to about 260° C. The reaction zone pressure is typicallyin the range of about 80 psia (552 kPa) to about 1000 psia (6895 kPa),more preferably from 80 psia (552 kPa) to about 600 psia (4137 kPa), andstill more preferably, from about 140 psia (965 kPa) to about 500 psia(3447 kPa).

[0078] For purposes of the present disclosure, certain terms areintended to have the following meanings.

[0079] “Active metal” refers to any metal that is present on a catalystthat is active for catalyzing a particular reaction. Active metals mayalso be referred to as catalytic metals.

[0080] A “promoter” is one or more substances, such as a metal or ametal oxide or metal ion that enhances an active metal's catalyticactivity in a particular process, such as a CPOX process or theFischer-Tropsch process (e.g., increase conversion of the reactantand/or selectivity for the desired product). In some instances aparticular promoter may additionally provide another function, such asaiding in dispersion of active metal or aiding in stabilizing a supportstructure or aiding in reduction of the active metal.

[0081] A “modifying agent” is one or more substances, such as a metal ora metal oxide or metal ion that modify at least one physical property ofthe support material that it is deposited onto, such as for examplestructure of crystal lattice, mechanical strength, morphology.

[0082] With respect to the catalytic reaction such as partial oxidationof light hydrocarbons such as methane or natural gas to producesynthesis gas or conversion of synthesis gas to hydrocarbons, referencesto “catalyst stability” refer to maintenance of at least one of thefollowing criteria: level of conversion of the reactants, productivity,selectivity for the desired products, physical and chemical stability ofthe catalyst, lifetime of the catalyst on stream, and resistance of thecatalyst to deactivation.

[0083] A precursor or a compound of a metal is a chemical entity, suchas, for example, a water-soluble metal salt, that contains the atoms ofthe metal (e.g., a catalytic metal, a catalytic promoter, or a modifyingagent) in an oxidation state that is not zero.

EXAMPLES

[0084] Preparation of Modified Alumina Supports

[0085] The unmodified alumina support was obtained as γ-Al₂O₃ sphereswith the following characteristics: a size in the range of 1.2 to 1.4 mm(average diameter of 1.3 mm.), a bulk density of 0.44 g/ml, a surfacearea and pore volume measure with N₂ adsorption of 143 m²/g and 0.75ml/g respectively.

Example A La₂O₃ Modified Al₂O₃

[0086] The γ-Al₂O₃ spheres described above were impregnated with aaqueous solution containing desired amount of La(NO₃)₃ so that the La₂O₃amount in the final material after drying and calcinations isapproximately 3% by weight. The Al₂O₃ spheres impregnated with La(NO₃)₃solution were dried in oven at 120° C. overnight and then calcined at1100° C. for 3 hr. The La₂O₃—Al₂O₃ spheres (Catalyst Support, CS-1) wereeither subject to further modifications or used directly as catalystsupport.

Example B La₂O₃ Modified Al₂O₃

[0087] The Al₂O₃ spheres described above were impregnated with asolution containing desired amounts of both La(NO₃)₃ and Al(NO₃)₃, andthen the obtained material was dried overnight in an oven at 120° C. for3 hrs and calcined at 1100° C. for 3 hrs.

Example C BaO Modified Al₂O₃

[0088] The Al₂O₃ spheres described above were impregnated with asolution containing desired amount of Ba(NO₃)₂ and then the obtainedmaterial was dried at 120° C. for 3 hrs and calcined at 1100° C. for 3hrs.

[0089] Table 1 lists the BET surface areas, pore volume, average porediameter, both measured by the BJH desorption method using N₂ as theadsorptive of commercially available unmodified γ-Al₂O₃ and modifiedAl₂O₃ catalyst supports. Surface area and pore size distribution areobtained on a Micromeritics TriStar 3000 analyzer after degassing thesample at 190° C. in flowing nitrogen for five hours. Surface area isdetermined from ten points in the nitrogen adsorption isotherm between0.05 and 0.3 relative pressure and calculating the surface area by thestandard BET procedure. Pore size distribution is determined from aminimum of 30 points in the nitrogen desorption isotherm and calculatedusing the BJH model for cylindrical pores. The instrument control andcalculations are performed using the TriStar software and are consistentwith ASTM D3663-99 “Surface Area of Catalysts and Catalyst Carriers”,ASTM D4222-98 “Determination of Nitrogen Adsorption and DesorptionIsotherms of Catalysts by Static Volumetric Measurements”, and ASTMD4641-94 “Calculation of Pore Size Distributions of Catalysts fromNitrogen Desorption Isotherms”. The initial surface area of the catalystis the surface area of the catalyst structure prior to contact ofreactant gas. The pore volume of the catalyst (N₂ as adsorptive) ismeasured and calculated using the method described above. Average poresize (diameter) based on N₂ adsorptive is calculated as 4 V/A. TABLE 1Surface area, pore volume and average pore diameter of support andcatalyst examples after different calcination temperatures of thesupport. Calcination Temp. of support, BET SA, Pore volume, Avg. poreExamples Composition ° C. m²/g ml/g diameter, nm control unmodifiedAl₂O₃ 1100 80 0.54 21 1200 16 0.19 45 A La₂O₃—Al₂O₃ 1100 89 0.63 21 120056 0.42 23 B La₂O₃—Al₂O₃* 1100 87 0.57 20 C BaO—Al₂O₃ 1100 66 0.44 21 2Rh/Sm₂O₃/La₂O₃— 1100 71 0.54 24 Al₂O₃

[0090] As shown in Table 1, modification of the Al₂O₃ with La₂O₃(Examples A and B) increases the surface area of the material aftercalcinations at 1100° C. (89 and 87 m²/g vs. 80 m²/g), while BaOmodified Al₂O₃ (Example C) shows lower surface area than unmodifiedAl₂O₃ (66 m²/g vs. 80 m²/g). The two La₂O₃ modified Al₂O₃ samplesprepared with different methods (with or without an aluminum oxidesolution) show no significant difference in surface area (89 m²/g vs. 87m²/g), but the Example A prepared with impregnating La(NO₃)₃-onlysolution possesses greater pore volume than the Example B and its porevolume is also greater than that of unmodified Al₂O₃ as well (0.63 ml/gvs. 0.54 ml/g). Doping Al₂O₃ with BaO (Example C) reduces the total porevolume, which decreases from 0.54 ml/g to 0.44 ml/g.

[0091] As the data in Table 1 shows, the higher calcination temperatureof 1200° C. resulted in a significant reduction in BET surface area andpore volume, with a simultaneous increase of the average pore diameterfor the unmodified alumina compared to the modified alumina. The BETsurface area, pore volume, and average pore diameter for unmodifiedalumina and Example A after calcination at 1200° C. are 16 and 56 m²/g,0.19 and 0.42 ml/g, 45 and 23 nm respectively. Without the presence ofthe modifying agent, the phase transfer to α-alumina is more prevalentin unmodified alumina at this higher calcination temperature, and thehigh calcination temperature causes some micropores to collapse andtherefore increase the pore sizes and decrease the surface area.

[0092] Modification of the Al₂O₃ with La₂O₃ does not change the porediameter distribution significantly, as shown in FIG. 1. The porediameter is ˜21 nm for the four catalyst supports listed in Table 2. Themost probable average pore diameter is about 17 nm for unmodified Al₂O₃and the two La₂O₃ modified Al₂O₃, while the most probable pore diameterof BaO modified La₂O₃ decreased to ˜13 nm (FIG. 1). The poredistribution curve of BaO modified Al₂O₃ (Example C) was shifted down tothe direction of smaller sizes (FIG. 1). Consequently, both the BETsurface area and total pore volume of BaO-Al₂O₃ are lower thanunmodified Al₂O₃.

[0093] The X-Ray Diffraction traces of unmodified Al₂O₃ and Examples A-Care shown in FIG. 2. After calcinations at 1100° C., the commerciallyavailable Al₂O₃ consists of gamma, theta, alpha phases (γ, θ, and αrespectively), with a significant presence of α phase. Compared withunmodified Al₂O₃, Examples A and B (La₂O₃ doped Al₂O₃) possesses less θand almost no α phases, based on the relative intensity of XRD signalsshown in FIG. 2. As the phase transformations of Al₂O₃ follow γ→θ→α withprogressive heating, it can be concluded that modifying the Al₂O₃ withLa₂O₃ inhibits the phase transformations from γ to θ to a, i.e.,modification of the Al₂O₃ stabilizes the structure of γ phase.Therefore, La₂O₃-Al₂O₃ (EXAMPLES A and B) maintains higher surface areathan unmodified Al₂O₃ and it also preserves the original pore structurebetter after high temperature calcination (see Table 1 and FIG. 1). Onthe other hand, doping the Al₂O₃ with BaO (EXAMPLE C) facilitate Al₂O₃phase transformation to α phase. The signals of XRD peaks due to a phaseAl₂O₃ are stronger and narrower in EXAMPLE C. (BaO modified Al₂O₃) asshown in FIG. 2, reflecting the presence of significant α-Al₂O₃ phase inlarger crystalline size compared to those present in unmodified Al₂O₃and La₂O₃-Al₂O₃ materials (Example A and B). The predominant α-Al₂O₃phase in BaO-Al₂O₃ explains that BaO-Al₂O₃ possesses a lower surfacearea than unmodified Al₂O₃ as BaO seems to de-stabilize the surfacestructure of γ-Al₂O₃ (Table 1).

[0094] Preparation of Catalysts

Example 1 4% Rh/La₂O₃-Al₂O₃

[0095] The La₂O₃-modified Al₂O₃ support material described as EXAMPLE Awas impregnated with a RhCl₃ solution and the catalyst was dried in anoven overnight at 120° C., calcined in air at 900° C. for 3 hrs and thenreduced in H₂ at 600° C. for 3 hrs. The Rh metal content in the catalystwas 4% by weight as calculated by mass balance. after drying andcalcination

Example 2 4% Rh-4% Sm/La₂O₃-Al₂O₃

[0096] The La₂O₃-modified Al₂O₃ support material obtained as EXAMPLE Awas impregnated with a Sm(NO₃)₃ solution. The material was dried in ovenfor overnight at 120° C. and then calcined at 1100° C. for 3 hrs. The Smcontent in the catalyst was 4 wt % Sm₂O₃ in the final material afterdrying and calcinations. The so-obtained Sm₂O₃/La₂O₃-Al₂O₃ catalystprecursor was impregnated with a RhCl₃ solution and the catalyst wasdried in oven for overnight at 120° C., calcined at 900° C. for 3 hr,and then reduced in H₂ at 600° C. for 3 hrs to metallic Rh form beforebeing charged into the reactor. The Rh metal content in the catalyst was4% by weight again determined by mass balance.

Example 3 4% Rh-4% Sm/La₂O₃—Al₂O₃

[0097] The catalyst sample was prepared similarly to Example 2, exceptthe calcination temperature used for Sm₂O₃/La₂O₃—Al₂O₃ spheres was 1200°C. (instead of 1100° C.). The Rh metal content in the catalyst was 4% byweight in the final material after drying and calcinations.

Example 4 2% Rh-4% Sm/La₂O₃—Al₂O₃

[0098] The catalyst sample was prepared similarly to Example 3(calcination of Sm₂O₃/La₂O₃—Al₂O₃ spheres at 1200° C.), except that theRh metal content in the catalyst was 2% by weight in the final materialafter drying and calcinations.

Example 5 1% Rh-4% Sm/La₂O₃—Al₂O₃

[0099] The catalyst sample was prepared similarly to Example 3(calcination of Sm₂O₃/La₂O₃—Al₂O₃ spheres at 1200° C.), except that theRh metal content in the catalyst was 1% by weight in the fmal materialafter drying and calcinations.

Example 6 4% Rh-4% Ru/La₂O₃—Al₂O₃

[0100] A rhodium alloy catalyst was prepared with the method describedin EXAMPLE 1. The La₂O₃ modified Al₂O₃ spheres (from EXAMPLE A) wereimpregnated with a solution containing both RhCl₃ and RuCl₃ such that toachieve 4 wt % for both Rh and Ru. The conditions for drying,calcination, reduction, are the same as those described in Example 1.The Rh and Ru content of the catalyst was 4 wt % for each metal in thefinal material after drying and calcinations.

Example 7 3.3% Rh/3.7% Sm on Co-Modified Alumina

[0101] A catalyst containing 3.3% Rh/3.7% Sm on a 2.19% Co modifiedalumina support was prepared as follows. Tri-lobe gamma alumina (SudChemie, Inc. Louisville, Ky.) was crushed into 20-30 mesh size(0.595-0.841 mm range). An aqueous solution of a cobalt nitrate wasapplied to the gamma alumina material and dried using a rotaryevaporator under vacuum and at a temperature of around 60° C. The dryingwas continued in an oven overnight at 90° C. The dried modified supportwas then heated up to 1100° C. in air and held at 1100° C. for fourhours. Aqueous solutions of samarium nitrate and rhodium chloride wererespectively applied to the support by impregnation, then theimpregnated modified support was calcined by heating up to 700° C. inair and held at 700° C. for two hours after each impregnation. The Rh/Smcatalyst was then reduced at 500° C. for three hours in a combined 300ml/min nitrogen and 300 ml/min hydrogen stream. The resulting catalysthad the following composition of 3.3% Rh/3.7% Sm on a 2.19% Co modifiedalumina support of 30-50 mesh size (0.297-0595 mm). Physical andmorphological characteristics of the support and the resulting catalystare given in Table 2. X-ray diffraction analysis of this sample revealedcorundum alumina (alpha) and CoAl₂O₄/Co₃O₄ spinel in a very distinctpattern. CoAl₂O₄ spinel was the major component. Apparently due to thesmall crystalline size, both Sm and Rh were undetectable.

Example 8 3.3% h/1.9% Sm on Mg Modified Alumina

[0102] A catalyst containing 3.3% Rh/1.9% Sm on a 5.1% Mg modifiedalumina was prepared by similarly like EXAMPLE 7 except that the cobaltnitrate solution was replaced by a magnesium nitrate solution. Theparticle size of resulting catalyst was again 30-50 mesh (0.297-0595mm). Physical and morphological characteristics of the support and theresulting catalyst are given in Table 2. Upon X-ray diffractionanalysis, this sample revealed corundum alumina (alpha) and MgAl₂O₄spinel components in a very distinct pattern. Again, the Sm and Rhcomponents were not found due to the small crystalline size.

Example 9 Rh/Sm on Si Modified Alumina

[0103] A catalyst comprising 3.7% Rh/3.7% Sm on Si modified alumina wasprepared by similarly like EXAMPLE 7 except that the Co nitrate solutionwas replaced by a sodium silicate solution (from Aldrich). The particlesize of resulting catalyst was again 30-50 mesh. Physical andmorphological characteristics of the support and the resulting catalystare given in Table 2. X-ray diffraction analysis indicates that the Siimpregnated sample was still mainly in the gamma alumina form, the Sicomponent being very difficult to identify. As in EXAMPLES 7 and 8, Smand Rh were not apparent due to the small crystalline size.

[0104] Catalyst compositions, metal surface area, and metal dispersionfor catalyst EXAMPLES 1-9 are summarized in the Table 2 below.

[0105] The metal surface area of the catalyst is determined by measuringthe dissociative chemical adsorption of H₂ on the surface of the metal.A Micromeritics ASAP 2010 automatic analyzer system is used, employingH₂ as a probe molecule. The ASAP 2010 system uses a flowing gastechnique for sample preparation to ensure complete reduction ofreducible oxides on the surface of the sample. A gas such as hydrogenflows through the heated sample bed, reducing the oxides on the sample(such as platinum oxide) to the active metal (pure platinum). Since onlythe active metal phase responds to the chemisorbate (hydrogen in thepresent case), it is possible to measure the active surface area andmetal dispersion independently of the substrate or inactive components.The analyzer uses the static volumetric technique to attain precisedosing of the chemisorbate and rigorously equilibrates the sample. Thefirst analysis measures both strong and weak sorption data incombination. A repeat analysis measures only the weak (reversible)uptake of the probe molecule by the sample supports and the activemetal. As many as 1000 data points can be collected with each pointbeing fully equilibrated. Prior to the measurement of the metal surfacearea the sample is pre-treated. The first step is to pretreat the samplein He for 1 hr at 100° C. The sample is then heated to 350° C. in He for1 hr. These steps clean the surface prior to measurement. Next thesample is evacuated to sub-atmospheric pressure to remove all previouslyadsorbed or chemisorbed species. The sample is then oxidized in a 10%oxygen/helium gas at 350° C. for 30 minutes to remove any possibleorganics that are on the surface. The sample is then reduced at 400° C.for 3 hours in pure hydrogen gas. This reduces any reducible metal oxideto the active metal phase. The sample is then evacuated using a vacuumpump at 400° C. for 2 hours. The sample is then cooled to 35° C. priorto the measurement. The sample is then ready for measurement of themetal surface. From the measurement of the volume of H₂ uptake duringthe measurement step, it is possible to determine the metal surface areaper gram of catalyst structure by the following equation.

MSA=(V)(A)(S)(a)/22400/m

[0106] where MSA is the metal surface are in m²/gram of catalyststructure;

[0107] V is the volume of adsorbed gas at Standard Temperature andPressure in ml.;

[0108] A is the Avogadro constant;

[0109] S is the stoichiometric factor (2 for H₂ chemisorption onrhodium);

[0110] m is the sample weight in grams; and

[0111] a is the metal cross sectional area.

[0112] As shown in Table 2, in which the metal in the equation isrhodium, the presence of samarium oxide (Sm₂O₃) helps to increase metaldispersion and metal surface area on the support Example A.

[0113] For the Rh-only catalysts with a rhodium metal dispersionmeasurement, i.e., Example 1 (4% Rh/La₂O₃—Al₂O₃) and Example 2 (4% Rh-4%Sm/La₂O₃—Al₂O₃), the presence of Sm₂O₃ almost doubles the Rh metaldispersion from 4.5% to 8.5%. The Applicants believe that additionaldeposit of Sm₂O₃ on the La₂O₃-modifed Al₂O₃ may further strengthen theinteraction of rhodium with the support and thus help Rh dispersion.TABLE 2 Catalyst Compositions for Examples 1-9 (on modified Al₂O₃),metal surface area, and rhodium dispersion. Metal Surface Promoter Area,-m²/g Metal CATALYST Modifying Active metal Loading, catalystdispersion - EXAMPLES agent loading, wt % wt % structure rhodium, % 1 La4% Rh 0% Sm 0.8 4.5 2 La 4% Rh 4% Sm 1.5 8.5 3 La 4% Rh 4% Sm 0.53 3.0 4La 2% Rh 4% Sm 0.35 5.5 5 La 1% Rh 4% Sm 0.35 8.0 6 La 4% Rh + 4% Ru 0%Sm 1.3 3.7 7 Co 3.33% Rh   3.7% Sm   3.3 — 8 Mg 3.3% Rh   1.9% Sm   7.7— 9 Si 3.7% Rh   3.7% Sm   0.63 —

[0114] Referring back to FIG. 1 which shows the pore size distributionof the catalyst Example 2, introducing Sm₂O₃ and/or Rh on La₂O₃—Al₂O₃caused almost no change to the probabilities of pores with diametergreater than 20 nm, as one compares the pore distribution curves ofsupport Examples A or B (La₂O₃—Al₂O₃) and catalyst Example 2 (4% Rh-4%Sm/La₂O₃—Al₂O₃); however, the probabilities of pores with diameter lessthan 20 nm decreased significantly. It is likely that Rh and Sm₂O₃coated preferentially on walls of <20 nm pores and reduced the porediameter of those pores on support surface.

[0115] The BET surface area, pore volume and average pore diameter weredetermined for catalyst Example 2 (see Table 1) and can be compared tothose of the support Example A that was used to make it. Both porevolume and BET surface area decrease compared to those of the support(89 versus 89 m²/g and 0.63 versus 0.54 ml/g respectively) whereas theaverage pore diameter increases (24 versus 21 nm), which is expectedafter deposition of both metals (Rh and Sm). The BET surface area isstill quite high despite metal deposition and additional calcinationsteps at temperatures greater than 800° C.

[0116] A temperature-programmed reduction was also performed forcatalyst Examples 1, 2 and 6. The TPR traces of 3 catalyst examplessupported on La₂O₃—Al₂O₃, one with rhodium (Example 1), one with rhodiumand Sm₂O₃ (Example 2), and one with a rhodium-ruthenium alloy (Example6). The reduction of Examples 1, 2 and 6 started at temperatures of 150,157, and 153° C. respectively. The reduction peak temperature was 177,183, and 183° C., respectively, again for Example 1, 2 and 6.

[0117] For the alloy-containing Example 6, the reduction peak shape isquite symmetrical. The single symmetrical reduction peak in the TPRtrace suggests that the Rh and Ru oxide species in this sample are inintimate contact or may even form a bulk compound in calcinations step;thus, H₂ may spillover from one site to sites of different nature oncethe reduction begins. As a result, only one single reduction peak wasobserved for the reduction of different oxide species (Rh and Ru).

[0118] For the Rh-only Examples 1 and 2, the presence of Sm speciescaused the reduction of Rh species to become more difficult—thereduction starts at higher temperature (150° C. vs. 157° C.) and thereduction peak position was also shifted from 177° C. to 183° C. forExample 2 with Sm₂O₃ addition. The difficulty of reduction for Example 2compared to the reduction of Example 1, indicates that the interactionbetween Rh species and support surface is stronger in the Example 2 [4%Rh-4% Sm/La₂O₃—Al₂O₃] than that in Example 1 [4% Rh/La₂O₃—Al₂O₃]. Again,the stronger Rh metal and support interaction in Example 2 maycontribute to its higher Rh dispersion on surface and metal surface areathan that of Example 1 (see Table 2).

Fixed Bed Reactivity Testing

[0119] These catalyst Examples 1-9 were tested with molecular oxygen andnatural gas as the hydrocarbon feed with a typical composition of about93.1% methane, 3.7% ethane, 1.34% propane, 0.25% butane, 0.007% pentane,0.01% C₅₊, 0.31% carbon dioxide, 1.26% nitrogen (with % meaning volumepercent). The hydrocarbon feed was pre-heated at 300° C. and then mixedwith O₂. The reactants were fed into a fixed bed reactor at a carbon toO₂ molar ratio of 1.87 or a O₂:natural gas mass ratio of 1.05 at gasweight hourly space velocities (GHSV) from about 161,000 to about635,000 hr¹. The gas hourly space velocity is defined by the volume ofreactant feed per volume of catalyst per hour. The partial oxidationreaction was carried out in a conventional flow apparatus using a 12.7mm I.D. quartz insert embedded inside a refractory-lined steel vessel.The quartz insert contained a catalyst bed (comprising of 2.0 g ofcatalyst particles, except for Example 7 where 1.65 g was used) heldbetween two inert 80-ppi alumina foams. The reaction took place forseveral days at a pressure of about 90 psig (722 kPa) for Examples 1-6and for several hours at a pressure of about 4 psig for Examples 7-9,and at temperatures at the exit of reactor between about 750° C. andabout 1200° C. All the flows were controlled by mass flow controllers.The reactor effluent as well as feedstock was analyzed using a gaschromatograph equipped with a thermal conductivity detector. Pressuresat the inlet and outlet on the reactor were measured by a differentialpressure transmitter which gives the overall pressure drop across thecatalytic bed by subtracting the pressure at the outlet from thepressure at the inlet.

[0120] The data analyzed include catalyst performance as determined byconversion and selectivity, and deactivation rate measured for some overa period of over 100 hours. The catalyst performances (CH₄ conversion,H₂ and CO selectivity) within a few hours after reaction ignition arelisted in the following Table 3 for Examples 1-8 and the observeddeactivation rates are listed in Table 4 for Examples 1, 2 and 6.Example 9 did not perform very well, and it should be noted that themetal surface area (ca. 0.63 m²/g catalyst structure) of this catalystExample 9 may have been too low to be an effective catalyst in thepartial oxidation of methane with oxygen. TABLE 3 Test data with CH₄conversion, CO and H₂ selectivity after 6 hours of reaction. CatalystGHSV, CH₄ CO H₂ Examples hr⁻¹ conversion, % selectivity, % selectivity,% 1 440,000 95 96 96 2 440,000 91 94 95  2* 440,000 94 97 97 3 675,00091 96 95 4 635,000 91 95 94 5 635,000 93 94 96 6 438,000 91 96 95 7161,000 95 96 89 8 175,000 96 97 90

[0121] TABLE 4 Deactivation measured over a time period from 24 to 104hours at a GHSV of about 440,000 hr⁻¹. Change in CH₄ Catalyst PressureDrop, conversion CO selectivity H₂ Selectivity Examples psi loss, %loss, % loss, % 1 0.68 3 1 1 2 0.02 2 1 0  2* 0.03 1 1 1 6 0.20 3 1 1

[0122] As shown in Table 3, all Examples have very good overallcatalytic performance. towards syngas production. Examples 1 and 2 havethe best methane conversion, whereas Examples 1, 2, 3, and 6 have verygood selectivity for H₂ and CO. The oxygen conversion (not shown) wasalso measured for all tests, and was above 99% for all Examples. Thebest overall catalytic performance is best with Examples 1 and 2 amongthe catalysts studied (listed in Table 2). From Table 3, Example 2 runsclearly show the best reactor performance. For direct comparisonrun-to-run, the data were obtained at the same time on stream, for mostruns from 6 to 104 hours after reaction initiation. The duplicate runsfor Example 2 are nearly equivalent (see Table 3), demonstratingcatalyst and reactor reproducibility.

[0123] Catalyst Examples 7 and 8 performance test results are also shownin Table. 3. A catalyst containing 3.9% Rh/4.2% Sm on a Co modifiedalumina support was prepared the same way as Example 7 and performedsimilarly to Example 7 in the laboratory scale fixed reactor testing. Acatalyst containing 3.7% Rh/3.8% Sm on a Mg modified alumina support wasprepared the same way as Example 8 and performed similarly to Example 8in the laboratory scale fixed reactor testing.

[0124] The change of the pressure drop over the course of the testsreported in Table 4 can be indicative of some catalyst deactivation.Increasing differential pressure may result from carbon depositionand/or poly-nuclear aromatic (PNA) formation on the catalyst surface orreactor system. Loss of methane conversion also can be indicative offormation of PNAs or PNA-precursors. As seen in Table 4, Example 2appears to deactivate at a slower rate than Examples 1 and 6. Both runsfor Example 2 show remarkable stability in pressure drop over timecompared to the other catalyst examples 1 and 6. It is likely thatExample 2 catalyst is less susceptibility to carbonaceous deposit.Example 1 catalyst exhibits higher loss of methane conversion thanExample 2. Example 6 catalyst exhibits equivalent loss of methaneconversion than Example 1.

[0125]FIG. 3 shows the plots of the methane conversion and productselectivity for a typical test run of catalyst Example 2, demonstratingthe great stability in partial oxidation of natural gas, with only 1%loss in methane conversion and product selectivity for the duration ofthe run (about 100 hours).

[0126] The examples and testing data show that the catalyst compositionsof the present invention represent an improvement over prior artcatalysts in their ability to resist deactivation over sustained timeperiods while maintaining high methane conversion and hydrogen andcarbon monoxide selectivity values. While the preferred embodiments ofthe invention have been shown and described, modifications thereof canbe made by one skilled in the art without departing from the spirit andteachings of the invention. The embodiments described herein areexemplary only, and are not intended to be limiting. Many variations andmodifications of the invention disclosed herein are possible and arewithin the scope of the invention. Accordingly, the scope of protectionis not limited by the description set out above, but is only limited bythe claims which follow, that scope including all equivalents of thesubject matter of the claims. The disclosures of all issued patents,patent applications and publications cited herein are incorporated byreference. The discussion of certain references in the Description ofRelated Art, above, is not an admission that they are prior art to thepresent invention, especially any references that may have a publicationdate after the priority date of this application.

What is claimed is:
 1. A process for producing synthesis gas comprisingpassing a hydrocarbon containing gas and an oxygen containing gas over acatalyst, under conditions effective to produce a gas stream comprisinghydrogen and carbon monoxide, wherein the catalyst comprises: (a) analumina support comprising at least one modifying agent; and (b) atleast one catalytically active metal deposited on said alumina support,and wherein the alumina support has undergone a high temperaturecalcination in the presence of a precursor of the at least one modifyingagent at a temperature equal to or greater than about 1000° C.
 2. Theprocess according to claim 1 wherein the high temperature calcination isperformed at a temperature greater than 1000° C.
 3. The processaccording to claim 1 wherein the alumina support has a surface area ofgreater than or equal to about 10 m²/g after said high temperaturecalcination.
 4. The process according to claim 1 wherein the catalystcomprises a metal surface area greater than 0.35 m²/g of the catalyst.5. The process according to claim 1 wherein the catalytically activemetal is selected from the group consisting of Group VIII metals,rhenium, tungsten, zirconia, molybdenum and mixtures thereof.
 6. Theprocess according to claim 1 wherein the catalytically active metalcomprises a metal selected from the group consisting of Rh, Ru, Ir, Reor mixtures thereof.
 7. The process according to claim 1 wherein thecatalytically active metal comprises rhodium.
 8. The process accordingto claim 1 wherein the catalytically active metal comprises a rhodiumalloy.
 9. The process according to claim 1 wherein the modifying agentcomprises at least one element selected from the group consisting ofaluminum, boron, silicon, gallium, selenium, rare earth metals, alkaliearth metals and transition metals, and their corresponding oxides andions.
 10. The process according to claim 1 wherein the modifying agentcomprises at least one element selected from the group consisting of La,Al, Sm, Pr, Ce, Eu, Yb, Si, Mg, Co, their corresponding oxides, theircorresponding ions, and combinations thereof.
 11. The process accordingto claim 1 wherein the modifying agent comprises one element selectedfrom the group consisting of aluminum, lanthanum, samarium, cobalt,magnesium, silicon, their corresponding oxides, their correspondingions, and combinations thereof.
 12. The process according to claim 1wherein the process exhibits a hydrocarbon conversion equal to orgreater than 80%, and a hydrogen selectivity equal to or greater than80%, under operating conditions of at least greater than or equal to 2atmospheres.
 13. The process according to claim 1 wherein the processexhibits a hydrocarbon conversion equal to or greater than 85%, and ahydrogen selectivity equal to or greater than 85%, under operatingconditions of at least greater than or equal to 2 atmospheres.
 14. Theprocess according to claim 1 wherein the process exhibits a loss inhydrocarbon conversion no greater than about 3% per day.
 15. The processaccording to claim 1 wherein the process exhibits a loss in hydrogenselectivity no greater than about 1% per day.
 16. A process forproducing liquid hydrocarbons comprising: (a) converting at least aportion of a feedstream comprising a hydrocarbon containing gas and anoxygen containing gas over a catalyst comprising an alumina supporthaving at least one modifying agent and at least one catalyticallyactive metal, under conditions effective to produce a gas streamcomprising hydrogen and carbon monoxide, wherein the alumina support hasundergone a high temperature calcination with a temperature equal to orgreater than about 1000° C. in the presence of a precursor of the atleast one modifying agent; and (b) reacting at least a portion of thegas stream from step (a) in a hydrocarbon synthesis reactor underconditions effective to produce C₅₊ hydrocarbons.
 17. The processaccording to claim 16 wherein the high temperature treatment is greaterthan 1100° C.
 18. The process according to claim 16 wherein the catalystcomprises a metal surface area greater than 0.35 m²/g of the catalyst.19. The process according to claim 16 wherein the catalytically activemetal is selected from the group consisting of Group VIII metals,rhenium, tungsten, zirconia, molybdenum and mixtures thereof.
 20. Theprocess according to claim 16 wherein the catalytically active metalcomprises a metal selected from the group consisting of Rh, Ru, Ir, Reor mixtures thereof.
 21. The process according to claim 16 wherein thecatalytically active metal comprises rhodium.
 22. The process accordingto claim 16 wherein the catalytically active metal comprises a Rh alloy.23. The process according to claim 16 wherein Step (a) exhibits ahydrocarbon conversion equal to or greater than 80%, and a hydrogenselectivity equal to or greater than 80%, under operating conditions ofat least greater than or equal to 2 atmospheres.
 24. The processaccording to claim 16 wherein Step (a) exhibits a loss in hydrocarbonconversion no greater than about 3% per day.
 25. The process accordingto claim 16 wherein Step (a) exhibits a loss in hydrogen selectivity nogreater than about 1% per day.
 26. The process according to claim 16wherein the alumina support has a surface area of greater than or equalto about 10 m²/g after said high temperature treatment.
 27. The processaccording to claim 16 wherein the modifying agent comprises at least oneelement selected from the group consisting of aluminum, boron, silicon,gallium, selenium, rare earth metals, alkali earth metals and transitionmetals, and their corresponding oxides and ions.
 28. The processaccording to claim 16 wherein the modifying agent comprises one elementselected from the group consisting of aluminum, lanthanum, samarium,cobalt, magnesium, silicon, their corresponding oxides, theircorresponding ions, and combinations thereof.